Over the past thirty years flexible intermediate bulk containers, commonly known as bulk bags, have come into widespread use for receiving, storing, transporting, and discharging flowable materials of all types. Although circular bulk bags are known, bulk bags are typically constructed from rectangular panels which are sewn together along their adjacent edges to define a bulk bag which is initially square or rectangular in horizontal cross section. Nevertheless, all bulk bags, whether initially square, rectangular, or circular in cross section tend to assume a circular configuration when filled due to the uniform pressure imposed by the contents of the bulk bag against the flexible fabric side walls thereof.
U.S. Pat. No. 4,903,859 discloses a bulk bag comprising four double layer side walls. Stiffeners formed from cardboard are inserted between the layers of the side walls thereby imparting sufficient rigidity to the container to permit its use with liquids. Although the bulk bag of the '859 patent has been generally well received, its utilization has been somewhat limited by the fact that it cannot be stacked.
Co-pending application Ser. No. 09/390,403 assigned to the assignee hereof (doing business as Composite Container Corp.) discloses an improvement over the bulk bag of the '859 patent. In application Ser. No. 09/390,403 there is disclosed a bulk bag having double layer side walls, and vertically extending corner pockets. Plywood sheets are received between the layers of the side walls, and wooden posts are received in the corner pockets to provide a bulk bag suitable for use with liquids which is stackable.
U.S. Pat. No. 5,076,710 discloses a baffle-type bulk bag wherein bridge panels or baffles are sewn across the four corners of a nominally rectangular bulk bag. The baffles prevent the side walls of the bulk bags from bulging outwardly when the bulk bag is filled, thereby retaining the filled bulk bag in a more or less rectangular cross-sectional configuration. The baffles may be provided with apertures which allow material to flow into and out of the corners of the bulk bag during filling and discharging operations.
Co-pending application Ser. No. 09/458,362, also assigned to the assignee hereof, discloses a baffle-type bulk bag which is stackable. In the bulk bag of application Ser. No. 09/458,362, triangular stiffeners are provided in the triangular corners of baffle-type bulk bags. The stiffeners may be formed from various materials including plastic panels, panels formed from corrugated paperboard and similar materials, etc. The stiffeners may be provided with apertures aligned with the apertures of the baffles thereby permitting the flow of material into and out of the bulk bag during filling and discharging operations.
Co-pending application Ser. No. 09/515,631, also assigned to the assignee hereof, discloses an octagon shaped bulk bag which is stackable. The use of the octagon shape in the construction of the bulk bag is advantageous in that it provides maximum stackability while eliminating the need for baffles and triangular stiffeners contained within the baffles.
The bulk bag disclosed in application Ser. No. 09/515,631 comprises eight double layer side wall portions. Each double layer side wall portion receives a stiffening panel which extends substantially the entire length and width of the side wall portion. The stiffening panels used in the side wall portions of the bulk bag may comprise corrugated plastic panels or similar panels made from other materials which are sufficiently resistant to bending.
The present invention comprises an improvement over the octagon shaped bulk bag disclosed in the above-identified '631 application. In accordance with the present invention, an octagon shaped bulk bag comprises a single layer side wall which is reinforced with belly bands. The belly bands comprise webbing of the type utilized in automobile and aircraft seatbelts, parachutes, cargo netting, and similar applications. Such webbing is typically manufactured by knitting, and comprises nylon, polyester, or similar stretch resistant, tough materials.
In the preferred embodiment of the invention, the belly bands extend around the interior of the single layer side wall and are secured thereto by stitching. Stiffening panels are in turn positioned inside the belly bands and are engaged with one another edge to edge so as to be self- supporting. The use of the stiffening panels renders the bulk bag stackable. In accordance with a second embodiment of the invention, the stiffening panels are secured in place by the belly bands. In accordance with a third embodiment of the invention, the belly bands extend around the exterior of the single layer side wall.